Virtual Memory in Operating Systems
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Questions and Answers

In demand paging, when is a page brought into memory?

  • At load time
  • When the process starts
  • When the system boots up
  • When the page is needed (correct)

    • What is the purpose of the valid-invalid bit associated with each page table entry?

  • To indicate if the page is memory resident (correct)
  • To indicate if the page is write-protected
  • To indicate if the page is swappable
  • To specify the page size

    • What is the role of a pager in demand paging?

  • To guess which pages will be used before swapping out
  • To bring in only those pages into memory that are needed (correct)
  • To allocate physical memory to pages
  • To manage the address space of a process

    • What happens if the valid-invalid bit in a page table entry is 'i' during MMU address translation?

    <p>A page fault occurs</p> Signup and view all the answers

    How does demand paging enable sparse address spaces with holes left for growth?

    <p>By bringing in only those pages into memory that are needed</p> Signup and view all the answers

    What is the main benefit of virtual memory?

    <p>Increased CPU utilization and throughput</p> Signup and view all the answers

    What does virtual memory allow in terms of address spaces?

    <p>Address spaces to be shared by several processes</p> Signup and view all the answers

    How is the virtual address space usually organized?

    <p>Start at address 0, contiguous addresses until end of space</p> Signup and view all the answers

    Which method can be used to implement virtual memory?

    <p>Demand paging</p> Signup and view all the answers

    What is the primary reason for using virtual memory?

    <p>To execute partially-loaded programs</p> Signup and view all the answers

    What is the main advantage of organizing the logical address space for stack to start at the max logical address and grow 'down' while the heap grows 'up'?

    <p>Maximizes address space use</p> Signup and view all the answers

    What is the primary benefit of demand paging compared to bringing the entire process into memory at load time?

    <p>Less I/O needed, no unnecessary I/O</p> Signup and view all the answers

    What functionality does the pager implement in demand paging?

    <p>Detects and loads the required pages into memory</p> Signup and view all the answers

    What is the purpose of the valid-invalid bit associated with each page table entry?

    <p>Indicates if the page is in memory or not</p> Signup and view all the answers

    What does the valid–invalid bit being set to 'i' on all page table entries indicate?

    <p>All pages are not in memory</p> Signup and view all the answers

    What enables sparse address spaces with holes left for growth and sharing of system libraries in virtual-memory systems?

    <p>Demand paging</p> Signup and view all the answers

    What does a lazy swapper do in demand paging?

    <p>Never swaps a page into memory unless it will be needed</p> Signup and view all the answers

    What new MMU functionality is needed to implement demand paging effectively?

    <p>Ability to distinguish between valid and invalid page references</p> Signup and view all the answers

    When are pages treated no differently from non-demand-paging systems during MMU address translation?

    <p>If they are already in memory</p> Signup and view all the answers

    How does demand paging handle a scenario where a page needed is not in memory?

    <p>It brings the not-in-memory page into memory from storage</p> Signup and view all the answers

    What is the primary benefit of using virtual memory?

    <p>Enables the execution of partially-loaded programs, leading to more efficient use of memory</p> Signup and view all the answers

    What does virtual memory enable in terms of address spaces?

    <p>Allows address spaces to be shared by several processes</p> Signup and view all the answers

    How is the virtual address space usually organized?

    <p>It starts at address 0 and has contiguous addresses until the end of space</p> Signup and view all the answers

    What is the role of a pager in demand paging?

    <p>It handles the transfer of pages between disk and main memory</p> Signup and view all the answers

    What happens if the valid-invalid bit in a page table entry is 'i' during MMU address translation?

    <p>The page is considered invalid and a page fault occurs</p> Signup and view all the answers

    In demand paging, when is a page brought into memory?

    <p>When a reference to a page is made and that page is not already in memory</p> Signup and view all the answers

    How does demand paging enable sparse address spaces with holes left for growth?

    <p>By allowing pages to be brought into memory only when needed</p> Signup and view all the answers

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